I'm looking for some information on how the SMS signalling protocols work.

From time to time I have an issue with my Sony Xperia X which runs Sailfish X OS and is connected to the Spark network. While I suspect the issue has something to do with the OS I'm sure there are other factors at play.

The problem is this, sometimes I send a text which keeps showing as sending on my phone, however the recipient has received the text.

It seems to only happen when I'm in a weak signal area and on 3 G.  Also the only phones I seem to have trouble with have been a Samsung Galaxy S8 Plus and another Samsung which I think is a Galaxy S7. All other phones seem to be OK, though my data set isn't all that large.

It would appear that when this happens my phone isn't getting a signal saying the text has been delivered. Is there such a signal? Is this signal handled differently by various OS's?

Sailfish OS is still maturing and I'd like to provide feedback to the developers but am trying to get as much information as I can first.

Any information or suggestions would be appreciated.

Thanks.